Supercritical Drying Semiconductor Substrate Cost Reduction
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Solution Overview
Problem
Supercritical drying methods for semiconductor substrates face challenges with high costs due to the need for thick, pressure-resistant chambers and potential deterioration of metal and polysilicon films when using organic solvents in a supercritical state, which affects the electric characteristics of semiconductor devices.
Innovation Solution
A supercritical drying method using a water-soluble organic solvent like IPA, where the solvent is brought into a supercritical state within a chamber, then transitioned to a gas phase, with an inert gas supply to prevent atmospheric exposure and maintain pattern integrity, reducing chamber thickness and material damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If supercritical CO2 fluid is used for drying, then surface tension is eliminated and fine patterns are protected, but chamber cost increases due to high pressure resistance requirements
Solution Approach 1:
The patent changes the drying parameter from supercritical CO2 (7.5 MPa) to supercritical water (22.06 MPa critical point), utilizing water's lower critical pressure to reduce chamber manufacturing costs while maintaining the supercritical state's surface tension-free drying capability that protects fine patterns
Solution Approach 2:
The patent uses water, which is inexpensive and readily available, as the drying solvent in supercritical state, replacing expensive CO2 supply systems and reducing overall process cost while achieving the same protective drying effect
2Ease of manufacture
If IPA is brought into supercritical state for drying, then chamber thickness is reduced and cost decreases, but metal and polysilicon films are etched causing deterioration in electric characteristics
Solution Approach 1:
The patent replaces organic solvents like IPA with water as the drying medium. Water is chemically inert to metal and polysilicon films at supercritical conditions, eliminating etching damage while maintaining the cost benefits of lower pressure requirements compared to CO2
Solution Approach 2:
The patent creates an inert supercritical water environment that does not react with or etch sensitive semiconductor films, unlike organic solvents that can chemically attack metal and polysilicon layers, thus protecting film integrity while achieving cost reduction
3Ease of operation
If conventional drying methods are used, then process simplicity is maintained, but fine patterns block due to surface tension of remaining liquid
Solution Approach 1:
The patent utilizes the phase transition of water to supercritical state, where surface tension becomes zero, allowing liquid to be replaced and evaporated without creating capillary forces that would cause pattern blockage, while maintaining operational simplicity through a single-chamber process
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method effectively reduces chamber costs and prevents damage to fine patterns and electric characteristics by eliminating surface tension and minimizing exposure to oxygen during the drying process.
Implementation Method 1
increasing a temperature inside the chamber to not lower than a critical temperature of the water-soluble organic solvent, thereby bringing the water-soluble organic solvent into a supercritical state
Implementation Method 2
decreasing a pressure inside the chamber and changing the water-soluble organic solvent in the supercritical state to a gas
Implementation Method 3
starting a supply of an inert gas into the chamber as the pressure inside the chamber decreases to atmospheric pressure
Data Source
AI summary
According to one embodiment, a supercritical drying method for a semiconductor substrate comprises introducing a semiconductor substrate, a surface of the semiconductor substrate being wet with a water-soluble organic solvent, to the inside of a chamber, hermetically sealing the chamber and increasing a temperature inside the chamber to not lower than a critical temperature of the water-soluble organic solvent, thereby bringing the water-soluble organic solvent into a supercritical state, decreasing a pressure inside the chamber and changing the water-soluble organic solvent in the supercritical state to a gas, thereby discharging the water-soluble organic solvent from the chamber, starting a supply of an inert gas into the chamber as the pressure inside the chamber decreases to atmospheric pressure, and cooling the semiconductor substrate in a state where the inert gas exists inside the chamber.